1. Field of the Invention
This invention relates to an image data transferring system and method for interfacing an image scanner and an image processor such as a personal computer, and more particularly to a system and method capable of rationally transferring image data read out from the image scanner to the image processor and command and control signals from the image processor to the image scanner by utilizing input-output lines of a general interface so as to fundamentally transfer various signals such as image data signals, status signals and other control signals between the image processor and the image scanner, without using a specific dedicated interface.
2. Description of the Prior Art
Image processing systems are being rationalized day by day as image processing techniques are improved. In particular, the image scanner has been decreased in size and weight while significantly heightening its performance. An image processor or image processing computer as well as the image scanner has evolved from a large-scale system to a high performance, small-scale system while markedly improving its performance.
In spite of the marked advance of the image processing computer and image scanner, data transferring systems for interfacing or linking the image processing computer and image scanner and the control means for controlling the data transferring system make scarcely any changes. To be specific, there has been so far used a dedicated signal transferring system or interface system for transferring the image data signals and the control and command signals between the image scanner and the image processing computer.
In general, as signal transferring or interfacing means, there are various interfaces such as an RS-232-C interface and GP-IB (general purpose interface bus) interface for linking the image scanner and the host image processing computer, a parallel interface such as SCSI, and a peculiar interface for the exclusive use of a flexible disk or floppy disk drive unit.
Since the RS-232-C interface mounted on the general purpose computer as a standard serial interface facilitates software description for controlling the input and output operation thereof, it can be easily handled, but suffers from the defect that information data is transferred at some-thousands of bits per second at most even if the transfer rate is set to the maximum. Therefore, in the case of the transfer of colossal image data necessary for reproducing a full color image composed of dots each depicted by either one of eight colors, the very slow transfer rate of the RS-232-C interface is disadvantageous for image processing.
Although the GP-IB interface has an advantage in that this interface make it possible to transfer information data between hardwares at a high speed, it requires software for exclusive use of input-output routines and complicated hardware such as an interface board to be set into the host computer, suggesting that it is not fit for a portable computer such as a stand-alone small-sized computer or a so-called note-type personal computer.
Other peculiar exclusive interfaces capable of being possibly miniaturized suffer from operational inefficiency in both software and hardware and lacking in versatility and practicability.
Attempts are now being made to use a bidirectional interface for bidirectionally transferring information data between the image processing computer and image scanner, but does not meet the needs for simplification of the hardware.
As a possible way of transferring signals between the image scanner and computer, there is proposed a system utilizing a Centronics interface commonly mounted in the computer for outputting printer data and control signals from the host computer to the printer in Japanese Patent Application Public Disclosure No. HEI 5-6238(A). The Centronics interface is widely applied to general purpose computers as a standard interface and has a function of transferring data in parallel between the computer and printer at a high speed.
To be more specific, the Centronics interface mounted in the host computer is provided with data output lines for forwarding data signals and control signals from the host computer to the printer, and handshake lines for feeding status signals representing the status of the printer to the host computer. This proposed system utilizes the handshake lines of the Centronics interface to transfer image data signals from the image scanner to the host computer, thereby materializing high-speed data transfer and miniaturization of the interface system.
Incidentally, the Centronics connector or interface boards with input-output ports are classified into some types having no compatibility according to the number of connector pins of, typically, Centronics interface boards of 36 pins, 25 pins, 24 pins and 14 pins. In addition, there is known a half-pitch Centronics connector of compact size for use in a portable computer. The connector pins in the connector board do not correspond to those in the different type Centronics interface boards in designation of signals to be transferred.
For instance, the 36-pin type Centronics connector has eight data lines [D0.about.D7] for outputting 8-bit data, handshake lines consisting of #1 port [STB (strobe)] correlating with the data ports and #10 port [ACK (acknowledge)], and message lines consisting of #11 [BUSY], #12 port [PE (paper end)], #13 port [SLCT (select)], #31 port [INIT (initialize)], #32 port [ERROR] and #36 port [SI (select-in)]. Since the ports of the handshake and message lines can transfer the signals from the printer to the host computer, it is possible to transfer a multiple-bit image data signal outputted from the image scanner to the image processing computer through these handshake and message lines. However, the handshake and message lines in the 25-pin Centronics connector consist of only five ports of ACK, BUSY, PE, SLCT and ERROR ports. Thus, an image scanner provided with the 36-pin type Centronics connector entailed a disadvantage such that it cannot be applied to the 25-pin or 14-pin type Centronics interface.
In general, a Centronics connector cable for a printer is made by bundling a number of wires, turning out to be large in volume and bulky to carry about together with a portable computer or image scanner. Besides, since the conventional connector cable of this type is short of flexibility, it is unsuitable for a self-propelling type portable image scanner capable of moving along the surface of a document by itself because it is hindered by the stiff connector cable when moving on the document to scan an image on the document, resulting in failure to scan the image.